add: 누락된 변수 추가

Author: Cyjin-jani

best-time-to-buy-and-sell-stock/Cyjin-jani.js

@@ -22,6 +22,7 @@ const maxProfit_naive = function (prices) {
 const maxProfit = function (prices) {
   let buyIdx = 0;
   let sellIdx = 1;
+  let profit = 0;
 
   while (sellIdx < prices.length) {
     let buyPrice = prices[buyIdx];